i just dug into the code that's triggered by the csv export button at the bottom of the page:

function NLReportWidgets_doExport(sExportType)
        {

            var sUrl = reportTable.oContentProvider.sUrl + "?id=" + reportTable.oContentProvider.sExecutionId
                               + "&reportaction=export" + sExportType
                    + NLReportWidgets_getGridDisplayPreferenceAsParam();

            var sRowRanges = "&visibleranges=" + (reportTable.oContentProvider.oHierarchy == null ? "" : reportTable.oContentProvider.oHierarchy.getVisibleRowRangesStringMergeAdjacent());

            sUrl += sRowRanges;
            NLReport_postURL(sUrl, "export_form");
        }